Device for determining the field of vision



v 1618 291-- b L. MAG'GIORE DEVICE FOR DETERMINING THE FIELD OF VISION Filed Mar ch 1:, 1926 Patented Feb. 22, 1927.

- UNITED STATES PATEE OFFER.

LUIGI EAGGIOBE, OF SASSARI, VITA LY, ASSIGNOR TO THE FIRM: CARL ZEISS, OI JENA,

' GERMANY.

DEVICE FOR DETERMINING THE FIELD OF VISION.

Application filed March 13, 1926, serial No. 94,607, and in Germany Harcl'r12, 1925.

The field of vision of an eye may be determined by bringin a surface of rotation,

which is, e. g. provi ed with a scale, before the eye to be tested,'the axis of which sur- 5 face of rotation traverses the eye, and by displacing, whilst the eye is looking straight ahead, on this surface of rotation in a plane perpendicular to the axis of this surface, a

mark until it is no longer perceived by the 1" eye to be tested.

The subject of the present invention constitutes a device for determinin the field of vision according to the aforesaid method,

. which, whilst being of simple and suitable construction, may be easily operated and which at the same time admits of easily varying the colour ofthe mark which is frequently of importance for the test. According to the invention this can be attained by using as a mark a luminous spot for whose production is employed a source of light, which is disposed on the axis of rotation of the surface on which the mark is to travel, and a 'rojection system which is face, forming the said surface of rotation. Besides, one suitably rovides in the vicinity of the source of ight a fixed reflector s stem, if necessary' with a second projection system through which a fixed luminous spot, also serving-as a mark, is thrown upon t e said projection surface. 7

The annexed drawing shows as an example a device according to the invention in a ongitudinal section.

' The device shown in the drawing contains a curved projection surfacaa which is by means of a pivot b rotatably supported in the head of a. pivot of a stand a. By means of a screw d it can be clamped in this head. The

pivot 12 carries a disc I), provided with a circle-division and opposed to an index a? fixed on the pivot of the stand 0, as well as an arm e at whose upper end is provided a head e with a reflector f and a projection system, consisting of a condenser g and a collective lens 9. The head a is provided with a hollovv pivot 6 about which a casing It may be rotated. In this casing there is fixed an electric glow lamp 5 and a secondpro ection system, consisting ofa condenser-j? and a collective lens i Both projection systems produce a bright luminousspot each on the bow a. Between the glow lamp 2' and. the collective lens j, on .the one-hand, and the glow rotatable about t e axis of the projection surlamp and the reflector f, on the other hand, thereis inserted in addition a colour filter k each. Both filters are constructed as interchangeable slides and are generally chosenof like colour. The casing It has a. surface It, provided with a circle-division and opposed to an index e fixed. on the head e. The interior of the surface 0 lies on aconical surface whose axis runs in the direction AA. With this axis, whichintersects the low '65 lamp i, also coincides the axis of the ho ow pivot 6 about which the casing 72. with the glow lam iand the projection system j is rotatab e. The an le of centre moi the aforesaid conical sur ace is so chosen that conjointly with the angle ,8, which the axis of the system 7' 7' embraces withthe axis of v the cone AA, it amounts to a little more than Thereby the angles, at which the light pencils traversing the lenses g and y" 7 are incident upon the surface a, become about 7 equal to the angles at which the corresponding pencils are reflected by this surface, so that the luminous spot can be seen as bright. as possible. At both its'ends the surface a 80 is provided with indentations a. p y

In order to determine withthe device the field of vision of an eye it is necessary to bring the eye to be tested into the centre of the. straight lines connectin the two inden- 35 tations. Whilst the eye is %ooking towards the fixed spot, producedat the centre of the bow by the system g 9 the user causes, by rotating the casing 72., the second spot to travel until it is just no longer perceived by the eye. Thereupon the position of-the' in dex a can be read off on the scale fixed on the surface It. According as the filters k are removed or remain in position it is possible,

to carry out the method in white or coloured light, whereby by a corresponding selection of the filters the colour may be chosen as desired. Moreover, by rotating the device about the pivot b with unchanged position of the eye, the size of the field of vision in 1 various planes may be determined, whereby the position-of the bow a is read oifat any one time on the scale fixed on the disc I).

I claim: Y

' 1. A device for determining the field of 1 5 vision, containing a holder, a source of light disposed on this holder, a curved projection surface of rotation, and a projection, system, adapted to receive light from the source of lightand to produce a'luminous spot on the said projection surface, the projection system being rotatable about an axis, traversing the source of 1i ht and intersecting the axis of the said pro ection system, and the axis of the said projection surface coinciding with the axis of rotation of the projection system.

2. A device for determining the field of vision, containing a holder, :3. source of light disposed on this holder, a curved projection surface of rotation, a rojection system, adapted to receive light from the source of light and to produce a luminous spot on the said projection surface, the projection system being rotatable about an axis, traversing the source of light and intersecting the axis of the said projection system, and a second projection system fixed on the holder, also adapted to receive light from the source of light and to produce a luminous spot on the projection surface, the axis of the said projection surface coinciding with the axis of rotation of theprojection system.

3. A device according to claim 2, containing a reflector system, inserted into the path of rays of-the second projection system, and adapted to deflect the rays, emerging from the source of light so as to strike on the projection surface.

4. A device according to claim 1 in which the said projection surface is a conical surface whose axis coincides with the axis of rotation of the projection system, this conical surface turning its concave side towards the source of light and its angle of centre being ap roximately complementary to the an le w ich the axis of the projection system embraces with the said axis of rotation.

PROF. LUIGI MAGGIORE. 

